"What is the attraction of terrorists to airplanes? Are they hypnotized by shiny objects?"
I'll try to play a psychiatrist to answer this question. I think it's two things that makes airplanes so attractive to terrorists, especially Islamic ones.
1) Blowing up of airplanes full of infidels in mid-air, hijacking airplanes, or using them as guided missiles like on 9-11 make for a terrible but surely spectacular crime that bound to get the world attention. All terrorists are craving for the world attention so they are attracted to airplanes as attention-drawers.
2) Maybe in Jihadist mind, dying in airplanes in the air is the surest way to paradise because in many religious traditions, sky, clouds, mountain tops or something above the earth is often associated with the place were Divine resides. Plus, when you are in the airplane in the air, you feel a bit beyond this world. Craving for something beyond this world is a human aspiration. In a perverse and twisted way, Jihadists also crave for something beyond this world. Since killing infidels in Islamic Jihad tradition is the road to paradise or heaven which is beyond this world, killing infidels in airplanes perhaps make it especially attractive to these brainwashed monsters.
I wonder if it's something like this: if it flies and is not a bird or an angel it is probably Satan's minions, so fair game.